Abstract: (Revised Abstract) DESCRIPTION This pilot research proposal is a conceptual break from a thirty year tradition characterizing the properties of single neurons in the inferior parietal lobule with increasingly complex behavioral tasks and analyses designed to isolate particular cognitive functions. Recent optical imaging studies have revealed the presence of multiple different topographic maps across the cortical surface of the inferior parietal lobule. The lowest resolution, and most robust is a representation of orbital gain fields; optic flow appears to be represented within this much as orientation is within retinotopy in V1. The proposal examines these two functions in inferior parietal lobe from a novel perspective- the neural circuit. There is simply no direct evidence in parietal cortex explaining how its sensory and gain field neuronal properties are generated. The molecular genetics of single neurons will be modified to measure the activity of selected neurons and populations of neurons. Standard microscopy will be used for population measures. Two-photon scanning microscopy will be use to directly compare cellular morphology and function. Specific neurons will be identified and studied over many days to assess the stability of their properties. This concept and the techniques for studying the circuitry is completely novel for association cortex; the use of modified molecular genetics of neurons in vivo in behaving animals has not been performed in any cortical area. The impact of these studies will be to open up cortex beyond striate in the behaving animal to circuit level analysis. In principle, the resolution of imaging can be extended to the level of the sub-cellular elements such as spines. In summary, this proposal is designed to understand properties of inferior parietal lobule neurons in terms of underlying neuronal circuits, much as investigators are now successfully exploring the circuit details of orientation tuning and color in primary visual cortex. Although the technical and conceptual issues are difficult, the expertise assembled is appropriate to the task. The successful outcome of these studies will be a substantial advance permitting direct visualization of the sub-cellular, cellular and circuit properties underlying the highest level cognitive functions such as attention, memory, intention and plasticity in the inferior parietal lobule.

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Thesaurus Terms:
biological model, brain imaging /visualization /scanning, cell morphology, ethology, neuroanatomy, neuron, parietal lobe /cortex, sensory cortex, technology /technique development
Macaca mulatta, Sindbis virus, behavioral /social science research tag, bioimaging /biomedical imaging, fluorescence microscopy, fluorescent dye /probe, green fluorescent protein, laboratory rat, single cell analysis, transfection /expression vector

Institution: RUTGERS THE STATE UNIV OF NJ NEWARK
249 UNIVERSITY AVE.
NEWARK, NJ 07102
Fiscal Year: 2006
Department: NONE
Project Start: 01-APR-2004
Project End: 28-FEB-2008
ICD: NATIONAL EYE INSTITUTE
IRG: ZEY1

Analysis of optic flow in the monkey

RM Siegel and HL Read

Center for Molecular and Behavioral Neuroscience, Rutgers University, Newark, NJ, USA.

Environmentally relevant stimuli were used to examine the selectivity of area 7a neurons to optic flow using moving, flickering dots. Monkeys performed a psychophysical task requiring them to detect changes in translation, rotational and radially structured optic flow fields consisting of collections of moving dots which are free of form cues. The neurons in area 7a were selectively responsive to all the different types of moving stimuli. Two types of tuning for motion selectivity were found. Some neurons were tuned to distinguish a particular direction of optic flow (e.g. radial expansion versus radial compression), while others were tuned to distinguish between different classes of optic flow (e.g. radial motion versus planar rotation). The latter tuning was unlike that reported for area MST by others and may represent a novel representation of optic flow. The response of these neurons to translating bars was compared to that of optic flow fields. There appeared to be no similarity in the tuning to the two types of motion. Furthermore, there does not appear to be an identity between the neurons that could be classified as opponent vector and those selective for radial optic flow. Area 7a is involved in the further analysis of optic flow beyond the cortical areas MT and MST and provides a novel representation of motion. These results are consistent with the neurons in area 7a utilizing motion for the construction of a spatial representation of extra-personal space.